The primary aim of this proposed project is to determine how closely changes in the apparent location of sound in the median sagittal plane corresponds to changes in the sound spectrum. This will entail several approaches: 1) The identification of spectral components important for localization of sound. 2) Assessment of the influence of training on the localization of sound in the medial sagittal plane. 3) Examination of the stimulus conditions that promote externalization. 4) Examination of the relative contributions of interaural spectral differences, interaural time differences and interaural sepctral differences toward accuracy in directional hearing.